Three water cannons, purchased by Mayor Boris Johnson from Germany, are to be delivered to London next week, British media report. The controversial street weapon, so far used nowhere in the country except Northern Ireland, are second-hand.

Boris Johnson’s administration decided to buy the £218,000
($370,971) machines in case there are any repeats of the London
riots of 2011, which caused millions of pounds worth of damage.

"Contract negotiations have been completed, and the water
cannons will be dispatched to London next week," a
spokesperson for the German federal police said on Friday.

A final decision on whether to use the cannons will be made by
Theresa May, the Home Secretary. The Metropolitan Police have
confirmed that they won’t use them until such permission is
obtained.

“We stress that these will not be deployed until or unless
the home secretary authorizes the use of water cannon in England
and Wales,” said the Met in a statement.

Once they arrive in the UK, the machines will need to be fitted
out to British specifications, which will take a few weeks, the
Guardian reported.

"These are an operational police assets and their movement is
subject to security considerations. Before they are ready to be
deployed a number of modifications need to be made. These include
the fitting of CCTV and adaptations to bring them into line with
the standards used in Northern Ireland. This is expected to take
a number of weeks," a spokesman for the mayor’s office said.

As for why London police would buy equipment that Germany now
views as redundant, Stephen Greenhalgh, Deputy Mayor for Policing
and Crime, told the BBC that the cannons are “perfectly
adequate”, having been subject to safety checks.

The sale to London comes as two German police officers went on
trial over the injury of a pensioner Dietrich Wagner, who lost an
eye after being hit by a jet of water in Stuttgart in 2011.

Ulrich Mann, Wagner’s lawyer, said that police in Germany were
now more cautious about their use as a result of the Stuttgart
protests.

“I would advise the London mayor against the purchase of
water cannons, especially if their use isn’t trained and
practiced regularly. They are dangerous tools that can lead to
grave injuries,” he said.

The purchase comes just two weeks after the eccentric London
mayor said he was prepared to be shot by one to prove water
cannons are safe. Police and crime commissioners from around the
country are already pushing for "smart water" to be used
in the water cannons. The ultraviolet dye can be added to the
water to allow police to trace anyone who was hit by the crowd
control weapon.

However, Nick Clegg, the deputy prime minister, said earlier this
month that he did not think water cannons were “the answer to
policing the streets of London.”

“The idea that in the riots, where people are scurrying down
small streets smashing windows and then rushing off - small
groups moving around in a very fluid situation - the idea that
great big lumbering second-hand German water cannons are somehow
going to be wheeled out and sort it out is, I think,
fanciful," Clegg said at his phone-in show on LBC.